Bobcat 751 Hydraulics just stop working, HELP!

[bradyr2003]

Gentelmen: I am working with a 1998 Bobcat 751. Borrowed from a family member and it had leaking Lift and Tilt spool seals. Replaced those, and what a job, but it was interesting. I wish I had know about those detent balls and spring. :confused2: Anyway, after replacing the spool seals, things worked great, for about ten minutes. When I picked up my first load of dirt the tilt would move very slow and did not have any power. When I tried to lift the load, very little movement. I then tried to back up and I had no drive. The HYD. oil is full, no noises like cavitation or anything, just won't move or lift anything. Maybe a plugged filter coming out of the oil tank? Any help someone might give would be appreciated.

Note: If I leave it shut off for several hours, the hydraulics will work for about 5 minutes and then quit again. Very frustrating.

 

[J_J]

Why did you replace the seals on the aux valve, was the valve leaking externally?

Was the drive train working normally.

On the detent and balls thing, you only had to asked.

This post sounds similar to another post I seen awhile back. Is this the same machine/post?

Maybe sucking air. Is your drive train driven by a pump and hyd motors? Is there a separate pump for the aux hyd.

I have a separate pump for my Case 1845.

 

[bradyr2003]

J_J

It was the main control valve spools for the bucket lift and tilt, not the aux. they were both leaking bad out of the backside of the spools. ( Spring end) both back seals were split in the middle. This was the first time they had been replace. (2400 hrs)

I not to familial with this thing, but I believe each wheel has a hydraulic motor. Not sure if there is a second pump for that or if the same (main) pump provides oil for both the drive and the working end of this thing?

This is my first post on this forum, and I read a post from a guy with what sounded like the same problem but i did not see that he resolved that problem. I did reply to his last comments and ask if he fixed the problem and what he found. I have not received a reply yet.

I appreciate you replying back and hope you or some other willing person/knowledgeable person can steer me in the right direction.

 

[J_J]

You will need a manual for your skidder, and a hyd gage would help out a lot.

Perhaps your Bobcat parts guy will print you the hyd schematics, and trouble shooting section.

 

[bradyr2003]

Downloaded a "Service Manual" today, several hundred pages bur did not contain the hydraulics trouble shooting pages, will be contacting the service about the missing pages. Anyway, had a 14 hour day at the plant today and will work on the machines Wednesday.

 

[bradyr2003]

Would fellow think that if a service manual was purchased, and it listed a Hydraulic troubleshooting guide in section 2-5, that it would actually have section 2-5 in the manual. WOW, the things people think they can get away with today. What happened to the honest people in this world?:confused2: